Field of the Invention
The present invention relates to an electric wire structure, an aircraft engine pylon, an aircraft, and a method for electromagnetic shielding of an electric wire.
Description of the Related Art
An aircraft is provided with a large number of electric wires (cables) for supplying electric power to various pieces of equipment or transmitting signals. For example, electric power generated by a generator installed in the engine is delivered to a power supply device provided in the airframe through an electric power line which is routed from the generator through the engine pylon to the airframe.
In an aircraft, provisions against lightning strikes are important. When lightning strikes, a high lightning current flows through the airframe. It is desirable to protect the electrical system from strong electromagnetic waves generated by the current.
Other than electromagnetic waves generated by lightning strikes, electromagnetic waves emitted from a radar of an airport control tower and electronic devices equipped in the aircraft also affect the aircraft.
Moreover, electric wires carrying alternating currents are not only affected by electromagnetic waves from the outside, but these electric wires also radiate electromagnetic waves and affect external devices.
In order to reduce the influence of electromagnetic waves, a twisted pair wire, a shielded electric wire having a shield member such as a metal braid wound around a core wire, etc. are commonly used.
There is also known a motor drive cable (Japanese Patent No. 5061114) in which return lines for returning to an inverter a high-frequency current leaking from a plurality of core wires which supply a drive current to a three-phase motor, are disposed between adjacent ones of the core wires.
The conventional electric wires provided with measures against electromagnetic waves, including twisted pair wires, shielded electric wires, and the electric wire shown in Japanese Patent No. 5061114, all have a jacket (sheath) which surrounds and integrates the core wire, the metal braid, the return line, etc. Having the jacket, the conventional electric wires provided with measures against electromagnetic waves are heavy in weight. It is desirable in aircrafts, for which weight reduction is a crucial issue, to implement measures against electromagnetic waves while minimizing the weight.
In addition, when provided with a jacket, the electric wire becomes less flexible and accordingly becomes less easy to route. The requirement for the ease of routing of an electric wire is high in an aircraft, as it is a large structure compared with a car etc., and an intricate narrow path continues over a long distance, for example, from the engine generator through the engine pylon to the main wing. Not only in aircrafts but also especially in large structures, there is a high requirement for the ease of routing of an electric wire.
When providing an existing electric wire with measures against electromagnetic waves, it is necessary to remove the existing electric wire and replace it with an electric wire provided with measures against electromagnetic waves, which takes enormous time and effort.
In view of the above problems, the present invention aims to provide an electric wire structure and a method for electromagnetic shielding of an electric wire which can keep down the weight and improve the ease of routing, as well as allows an existing electric wire to be easily provided with measures against electromagnetic waves.